The woodland Pío XI is shoving aside is Magellan­ic rain forest—not the dark, canopy-rich rain forest of the tropics, but the kind of matted, windblown bonsai you see at tree line in the mountains. And no wonder. The fjords and islands of Chilean Patagonia take the brunt of the prevailing westerlies that wail across the southern seas. Here in the heart of the roaring forties, the wind can blow with almost constant ferocity. Rain and snow can fall all year round.

No place on the planet is fully at rest. Only time—unimaginable stretches of time that conceal from human eyes the dynamic natural forces shaping the Earth—creates the illusion of stasis. But sometimes, if you're lucky, you come upon a place where time seems compressed, where you can feel in your bones how kinetic even geol­ogy really is.

The glacier-carved coast of Chile is such a place. Here the Earth's energy seems almost palpable. Tectonic plates are spreading and then diving under this fringe of the continent, lifting the Andes and creating a geologically volatile zone. From the interior ice fields, glaciers such as Pío XI—short, brutal rivers of ice—descend swiftly to the sea. Offshore, the upwelling of the Peru Current is a fountain of aquatic life. The shoreline, divided by a labyrinth of waters, stretches more than 50,000 miles. This Patagonia differs utterly from the one that name usually conjures—a land of broad pampas. This Patagonia belongs to sea and ice.

At the heart of this wild region lies Bernardo O'Higgins National Park. More than 200 miles from end to end, the park encompasses Patagonia's Southern Ice Field, which with its northern counterpart forms one of the largest expanses of glacial ice outside the polar regions.

There is no coming overland to Bernardo O'Higgins, and no flying in either. The only way in is by water, intricately, through a maze of deepwater fjords that ultimately leads to the snout of Pío XI. There glacial thunder fills the air—cracking, resonant reports from deep in the ice field as well as duller but more profound detonations caused by the calving of bergs from Pío's snout. Those explosions end with the hiss of new waterfalls and spilling ice shards.

At the ragged seam where glacier meets rain forest, Pío fills the sky, a mountain of ice towering toward the midday sun. Nearby, the glacier is almost cormorant black, then petrel gray. Farther off, higher up, the ice turns white and then a hundred impossible species of blue.